<p>
  <%= form.label :name, "名称:" %><br />
  <%= form.text_field :name %>
</p>
<p>
  <%= form.label :parent_id, "父目录:" %><br />
  <%= form.select :parent_id, Category.select_options %>
</p>
<p>
  <%= form.label :rank, "排序:" %><br />
  <%= form.text_field :rank %>
</p>
